This invention relates to a method of fitting a plate member with at least one supportive or protective member of a synthetic resin by molding the resin with insertion of a marginal region of the plate member in the mold cavity. A typical example of the plate member is a glass plate for use as a vehicle window glass which can be pulled up and down.
In manufacturing window glasses for openable windows of automobiles, a shaped glass plate is fitted with holders to be coupled with a window regulator mechanism. Currently the holders are usually made of a synthetic resin. Shaped glass plates for some windows are fitted with protective or cushioning moldings around edges of the plates.
One way of fitting a glass plate with a plastic member, which may be any of the aforementioned holders and moldings, is forming the plastic member as a separate part and then attaching that member to the glass plate by either an adhesive means or a mechanical fastening means. However, this is rather inconvenient for industrial manufacturing. In the case of using an adhesive, usually the plastic member needs to be formed with projections to prevent the adhesive from extending into unnecessary areas and minute undulations to augment the strength of adhesion. Besides, it takes a relatively long time to cure or solidify the applied adhesive, and in an extreme case there arises a discrepancy of curvature between the glass plate and the plastic member so that the obtained window glass does not fit in the window. Further, there is some possibility of detachment of the plastic member by deterioration of the adhesive bond. In the case of using a mechanical fastening means it is necessary to bore holes in the glass plate. The boring weakens the glass plate, and the tight clamping of the fastening means is liable to produce irregular stress around each hole in the glass plate.
Another way is accomplishing molding of the plastic member and bonding of the molded member to the glass plate simultaneously. That is, in molding the plastic member a predetermined region of the glass plate is kept inserted in the mold cavity. In general this method is advantageous over the method of attaching a separately formed member to a glass plate in respect of productivity and cost. Furthermore, it is possible to simplify the shape of and reduce the size of the plastic member. This very favorable for window glasses for recent automobiles in view of the current trend toward utilization of the space in a door frame for installation of various instruments or accessories and fitting of a door inner panel with various functional elements. However, in this method it is important to take an appropriate measure to ensure firm and reliable bonding of the molded resin member to the glass plate. In recent automobiles there is a trend toward enlargement of windows and reduction in the thickness of window glasses, and in hardtop cars and sashless cars which are increasing it is inevitable that a greater force acts on the window glass holders coupled with guide channels. Therefore the holders are required to very firmly adhere to the window glass.
JP-UM A No. 61-186619 shows fitting a vehicle window glass with holders by forming a hole or a recess in the glass plate in each marginal region where a holder is to be attached and performing injection molding of a synthetic resin to form the holders such that a portion of the injected resin enters the holes or recesses in the glass plate. However, this method entails the extra operation of machining the glass plate to form the holes of recesses, and the adhesion of the holders to the glass plate is not augmented in areas other than the holed or recessed areas.
JP-A No. 59-199228 shows producing an automobile opera window glass by fitting a cross-sectionally U-shaped covering formed of a rubber or a soft resin around the periphery of the glass plate, then performing injection molding of a hard resin or as to form a resin frame or molding over the elastic covering and subsequently removing edge portions of the elastic covering protruding from the overlying resin molding. The provision of the elastic covering is effective for prevention of appearance of burrs in the resin molding. However, the interposition of the elastic covering does not seen to be effective for enhancement of the strength of bond between the hard resin molding and the glass plate.
GB-A No. 2,192,658, which shows fitting a vehicle window glass with holders by inserting protruding marginal regions of the glass plate into the mold in molding the holders, proposes to form some projections in the edge portion of each of the aforementioned marginal regions so as to locally increase the thickness of the glass plate. Although a mechanical or thermal treatment of the glass plate is needed to form the proposed projections, the holders bond very securely to the glass plate as the thickness increased edge portion of the plate is embedded in each holder molded in situ.